This is so ridiculous...they DO state that lol. They also state that amps that come close to doubling in power have shown to work well, too...so what? Are they supposed to lie and say they don't work well?.

No. ..But nor should they be calling such amps the "Gold Standard". .. And now after reading Arnyk's comments about the improbability of an amp actually accomplishing this glorious 8 to 4 ohm "doubling down" I wonder if what these manufacturers (like Anthem) are doing is simply understating their 8ohm power so as to APPEAR to be doubling into 4ohm. What could be easier and who would call them on this? ..If Stereophile reviewed the amp and measured it, they'd simply report that the amp hits both it's stated 8 and 4 ohm specs and managed a few extra watts into 8 ohms.

And it's not like Magnepan is the only speaker manufacturers who makes this sort of bogus amplifier recommendation . I owned a pair of Vandersteen 3A Sigs for years (and loved them). In the owners manual Richard Vandersteen makes the same sort of statements about his speakers performing best w/ amps that double their power into 4ohms (he doesn't say "close" to doubling, he says "doubling"). AND he goes on to state that speaker cable selection is also very important as well as speaker cable break-in (oy vey).

... And now after reading Arnyk's comments about the improbability of an amp actually accomplishing this glorious 8 to 4 ohm "doubling down" I wonder if what these manufacturers (like Anthem) are doing is simply understating their 8ohm power so as to APPEAR to be doubling into 4ohm. What could be easier and who would call them on this? ..If Stereophile reviewed the amp and measured it, they'd simply report that the amp hits both it's stated 8 and 4 ohm specs and managed a few extra watts into 8 ohms.

...

Many people seem to forget that a specification is merely a claim, not a measurement. If you make an amplifier that puts out (all figures to follow are continuous RMS from 20-20KHz w/<0.01% THD) 180 watts into 8 ohms and 200 watts into 4 ohms, how you rate it will depend upon to whom you are selling it and your marketing strategy. If you are selling it as an audiophile product, you slap a thick aluminum case on it and rate it as 100 watts into 8 ohms and 200 watts into 4 ohms and charge three or four times as much as the model that you sell to regular folks, which you put in a sheet metal case and rate as putting out 180 watts into 8 ohms and 200 watts into 4 ohms. The thick aluminum case will make the one weigh more, which is another factor that some audiophiles use in determining which amplifier they believe is better.

God willing, we will prevail in peace and freedom from fear and in true health through the purity and essence of our natural fluids. God bless you all.

Originally Posted by Jack D Ripper
Many people seem to forget that a specification is merely a claim, not a measurement. If you make an amplifier that puts out (all figures to follow are continuous RMS from 20-20KHz w/<0.01% THD) 180 watts into 8 ohms and 200 watts into 4 ohms, how you rate it will depend upon to whom you are selling it and your marketing strategy. If you are selling it as an audiophile product, you slap a thick aluminum case on it and rate it as 100 watts into 8 ohms and 200 watts into 4 ohms and charge three or four times as much as the model that you sell to regular folks, which you put in a sheet metal case and rate as putting out 180 watts into 8 ohms and 200 watts into 4 ohms. The thick aluminum case will make the one weigh more, which is another factor that some audiophiles use in determining which amplifier they believe is better.

No. ..But nor should they be calling such amps the "Gold Standard". .. And now after reading Arnyk's comments about the improbability of an amp actually accomplishing this glorious 8 to 4 ohm "doubling down" I wonder if what these manufacturers (like Anthem) are doing is simply understating their 8ohm power so as to APPEAR to be doubling into 4ohm. What could be easier and who would call them on this? ..If Stereophile reviewed the amp and measured it, they'd simply report that the amp hits both it's stated 8 and 4 ohm specs and managed a few extra watts into 8 ohms.

And it's not like Magnepan is the only speaker manufacturers who makes this sort of bogus amplifier recommendation . I owned a pair of Vandersteen 3A Sigs for years (and loved them). In the owners manual Richard Vandersteen makes the same sort of statements about his speakers performing best w/ amps that double their power into 4ohms (he doesn't say "close" to doubling, he says "doubling"). AND he goes on to state that speaker cable selection is also very important as well as speaker cable break-in (oy vey).

I see...well I'm sure Arny is correct in what he says...I was mostly addressing your comment that, "So flipping through my AudioAdvisor mailer here in my den I see that Magnepan would regard the Bryston 4Bsst ($5000), Musical Fidelity M6 ($3500), and Parasound A31 ($3000) as unsuitable amps for their speakers." I can assure you that Magnepan makes no such claim or implication. Beyond that, all I can say is that I have communicated with Wendell and others at Magnepan going on a decade now, and this is not a topic where they make definitive claims other than stating that you need an amp/receiver that is stable into 4ohm.

Yeah, those little ICE modules are fantastic. I think it's more that Magnepan isn't up to date on them and/or don't have any practical experience with the class D stuff. As you and I both know, though, they work great. Stable into 2ohms and drive the panels just fine.

Many people seem to forget that a specification is merely a claim, not a measurement. If you make an amplifier that puts out (all figures to follow are continuous RMS from 20-20KHz w/<0.01% THD) 180 watts into 8 ohms and 200 watts into 4 ohms, how you rate it will depend upon to whom you are selling it and your marketing strategy. If you are selling it as an audiophile product, you slap a thick aluminum case on it and rate it as 100 watts into 8 ohms and 200 watts into 4 ohms and charge three or four times as much as the model that you sell to regular folks, which you put in a sheet metal case and rate as putting out 180 watts into 8 ohms and 200 watts into 4 ohms. The thick aluminum case will make the one weigh more, which is another factor that some audiophiles use in determining which amplifier they believe is better.

What is the deal with correlating "audiophile" with idiot? Is it not possible to see oneself as an audiophile and also not be ignorant of prudent choices in gear and accessories?

Many people seem to forget that a specification is merely a claim, not a measurement. If you make an amplifier that puts out (all figures to follow are continuous RMS from 20-20KHz w/<0.01% THD) 180 watts into 8 ohms and 200 watts into 4 ohms, how you rate it will depend upon to whom you are selling it and your marketing strategy. If you are selling it as an audiophile product, you slap a thick aluminum case on it and rate it as 100 watts into 8 ohms and 200 watts into 4 ohms and charge three or four times as much as the model that you sell to regular folks, which you put in a sheet metal case and rate as putting out 180 watts into 8 ohms and 200 watts into 4 ohms. The thick aluminum case will make the one weigh more, which is another factor that some audiophiles use in determining which amplifier they believe is better.

What is the deal with correlating "audiophile" with idiot? Is it not possible to see oneself as an audiophile and also not be ignorant of prudent choices in gear and accessories?

Ask the manufacturers. High end audio gear with thick metal plates with no technical purpose is old news.

Ask the manufacturers. High end audio gear with thick metal plates with no technical purpose is old news.

I guess my definition of audiophile is different than what others typically consider them to be in this forum. I very much enjoy the pursuit of hi-fi, but I've never bought a boutique cable or focused on thick metal plates with no technical purpose in my life.

Originally Posted by SummaYeah, those little ICE modules are fantastic. I think it's more that Magnepan isn't up to date on them and/or don't have any practical experience with the class D stuff. As you and I both know, though, they work great. Stable into 2ohms and drive the panels just fine.

Exactly, they never respond to email and to get them on the phone good luck!

Yeah, those little ICE modules are fantastic. I think it's more that Magnepan isn't up to date on them and/or don't have any practical experience with the class D stuff. As you and I both know, though, they work great. Stable into 2ohms and drive the panels just fine.

What most fail to realize is that something that works great may be completely different than something that sounds great. Other than for subwoofer duties, I have yet to hear good sounding class D equipment. That includes the ICE modules and Rotel's digital amplifiers, both are some of the best representation of class D available today.

Yeah, those little ICE modules are fantastic. I think it's more that Magnepan isn't up to date on them and/or don't have any practical experience with the class D stuff. As you and I both know, though, they work great. Stable into 2ohms and drive the panels just fine.

What most fail to realize is that something that works great may be completely different than something that sounds great. Other than for subwoofer duties, I have yet to hear good sounding class D equipment. That includes the ICE modules and Rotel's digital amplifiers, both are some of the best representation of class D available today.

Perhaps your ears are abnormal? Subjective opinions are only so useful. I've had good experience with my class D amps on the other hand. So you fail to realize IMHO....

To be honest when I compare Class D vs Class A or class A/B I will take class A or Class A/B any day of the week

I'm a huge fan of A/B amps. They sound great! Every amp that I have ever owned, or personally designed and built was A/B. I bias the first watt, or two into class A to keep the MOSFETs always open (80mA-150mA per device). I've practically listened to everything out there on the market and nothing was able to convince me to switch to class D, H, or even B amplifiers. When it comes to amplifiers, the true and tried formula has remained the same for decades and I don't see it changing anytime soon: jfet input, bipolar voltage stage, MOSFET output, class A/B.

What most fail to realize is that something that works great may be completely different than something that sounds great. Other than for subwoofer duties, I have yet to hear good sounding class D equipment. That includes the ICE modules and Rotel's digital amplifiers, both are some of the best representation of class D available today.

Well, thankfully the audio police don't force people to choose which amps to use in their rigs

I have my Butler amps and my Peachtree Nova and really enjoy both. My Butler 5150 has been the backbone of my home theater rig for nearly a decade now, and it's a great match with Maggie. The Nova is a component of convenience, but it truly surprised me how well it drove the Maggies. I just feel fortunate to have such amazing sound.

What most fail to realize is that something that works great may be completely different than something that sounds great. Other than for subwoofer duties, I have yet to hear good sounding class D equipment. That includes the ICE modules and Rotel's digital amplifiers, both are some of the best representation of class D available today.

Let us know when you do a bias controlled comparison. I'd be interested in the result.

Also a class B has less distortion than a so called 'class AB' that is biased into class a for a few watts.
You are mistaken that this practice is always keeping the fets 'open'.

Absolutely. MOSFETs for life. And now we get back to the same old stock answer I keep having to give out around here: Just because something is more linear, or lower in distortion (from what we're measuring anyway), it does not mean that it sounds better. MOSFETs sound like vacuum tubes. And those sound great. But with MOSFETs we can build more serious amplifiers with other beneficial attributes, like high slew rate, etc.

This forum constantly surprises me with such narrow thinking. This is not how real engineers and scientists work. We can maybe measure a hundred parameters tops in regards to output devices. We can probably theorize a couple thousand different possibilities. But in reality, there's an infinite amount of parameters possible. Just because BJTs measure more linear does not mean that MOSFETs don't have other attributes which are significantly superior to BJTs that we haven't even thought of yet, let alone have the capability to measure.

I've listened to MOSFETs and BJTs and to me MOSFETs sound like vacuum tubes. I like that. I don't like BJTs. And to my ear, class B sounds gritty and lifeless. And of course biasing slightly into class A keeps the MOSFETs open. If you have the divice specifications, you can bias them so.

And now we get back to the same old stock answer I keep having to give out around here: Just because something is more linear, or lower in distortion (from what we're measuring anyway), it does not mean that it sounds better.

That is true and the actual reason is that "sounds better" is strongly conditioned or if you will biased, by what you are used to hearing.

This explains why such horribly colored, nonlinear and objectionably noisy media such as LPs are still preferred by some. It is what they are used to.

Quote:

MOSFETs sound like vacuum tubes.

Simply not true. It is possible to build MOSFET, bipolar, and tubed amplifiers that will pass a straight wire bypass test. Doing this with MOSFETs and bipolar devices is easy, while doing it with tubes is expensive and harder to do. IOW they can all be sonically transparent, with tubes being far less likely to be that good. But it can be and has been done.

The problem with the statement above is that since they can all be sonically transparent, they have no inherent sound. Therefore they cannot sound like each other or anything else. They have no characteristic sound that can be always identified with them.

Quote:

And those sound great. But with MOSFETs we can build more serious amplifiers with other beneficial attributes, like high slew rate, etc.

Slew rate as a concept has been totally discredited. It was always something that has been around for a long time - namely excess nonlinear distoriton at high frequencies. So it was misnamed to begin with.

Quote:

This forum constantly surprises me with such narrow thinking.

If that exists it may come from picking and choosing what you care to look at.

Quote:

This is not how real engineers and scientists work.

This post suggests to me that it is not written by a person with any special understanding of how science and engineering work.

Quote:

We can maybe measure a hundred parameters tops in regards to output devices. We can probably theorize a couple thousand different possibilities. But in reality, there's an infinite amount of parameters possible. Just because BJTs measure more linear does not mean that MOSFETs don't have other attributes which are significantly superior to BJTs that we haven't even thought of yet, let alone have the capability to measure.

This appears to be an example of trying to control the situation by making it more complex than it needs to be. I don't know how one gets to 100 relevant parameters when measuring the electrical parameters of output devices. Either the manufacturers are hiding something or there aren't 100 relevant parameters because their spec sheets don't list anything like 100 relevant parameters.

For example this data sheet which is fairly typical has about 24 electrical parameters:

I've listened to MOSFETs and BJTs and to me MOSFETs sound like vacuum tubes. I like that. I don't like BJTs. And to my ear, class B sounds gritty and lifeless. And of course biasing slightly into class A keeps the MOSFETs open. If you have the divice specifications, you can bias them so.

It is true that it may take uncommon skills to do appropriate bias-controlled listening tests, but that's what it takes to hear the objective truth about them.

This forum constantly surprises me with such narrow thinking. This is not how real engineers and scientists work..

I'll be darned. You aware, I assume, that some of the people who post here are real engineers and scientists.

This is simply a failure to communicate. There is a lack of quantifiers and qualifiers that causes the disagreement. It should be, "this is not how real engineers and scientists work who are the few bat-**** crazy ones who have gone senile or got their degrees from diploma mills." See, now it makes sense and is perfectly correct. Next, we can hear how real scientists are not so narrow-minded that they disavow the idea of turning lead into gold or flying on a magic carpet. The real scientists, of course, who are the few bat-**** crazy ones who have gone senile or got their degrees from diploma mills.

Science is all about limitations. As long as one knows nothing, then anything is possible as far as one knows. The more one knows, the more one knows that many things are not possible. In other words, the more one knows, the more the possibilities become more narrow and confined. That people cannot fly without the aid of devices is a limitation on what is possible, and a failure to understand this limitation is not a virtue.

God willing, we will prevail in peace and freedom from fear and in true health through the purity and essence of our natural fluids. God bless you all.

Hi Arnyk!!!!! Hi!!! It's been known since dinosaurs roamed the earth that field effect transistors sound like vacuum tubes. They even operate on the same principals and MOSFETs can replace tubes in most amplifiers with minimal circuit changes.

Intro: Electricity and Hydraulics
Lots of people don't understand electricity, but they do understand plumbing. Hydraulics provides a good analogy in understanding basic electrical flow. Wire is a pipe. Water pressure is voltage. Water flow is electrical current. Lakes and storage tanks are capacitors. Diodes are one-way valves. Tubes and transistors are faucets.
The entire power circuitry of an amplifier can be seen as a community water system. The sun, driving the weather cycle, deposits water on the landscape, and it collects in a lake behind a dam. The community draws water as needed through pipes. In the winter, the rain collects in the lake, and the water pressure increases as it fills. In the summer the water level falls, and so does the pressure. When the community draws more water than usual, the level goes down more, and it often takes more than one season to build it back up.

In an amplifier, your utility, house wiring, power cord, and transformer provide the rain. The capacitor bank is the reservoir. The capacitors receive electrical charge every 1/120th of a second, reflecting two pulses of current from the transformer for every cycle of the 60 Hz sine wave provided by the power company.

These pulses are of relatively short duration, and it is up to the power supply capacitors to store energy during the 6 millisecond or so electrical drought that occurs between charge pulses. We want a constant voltage (water level) from our power supply, and this is usually achieved by the use of large capacitors which store more charge, and large transformers which provide as much charge as is needed. You get the idea.

Since we are not designing amplifiers here, but rather trying to get a handle on what constitutes quality in a market full of hype, I want to talk about some general ideas and comment on some of the common approaches used by manufacturers. Understand that we simply want a constant, noise-free, voltage to be available from a power supply, regardless of how much demand we place on it.

Bigger and heavier is better. Bigger transformers and wires load down less. Big capacitors hold more charge.
Is there such a thing as too big? Certainly there are diminishing returns as we get bigger. When a transformer is delivering 1 watt to a preamp circuit, going from a thousand watt rating to two kilowatts isn't going to buy you much improvement. This consideration is not much of a deterrent to the average audiophile, however.

Power transformers
The best power transformers are toroids, with donut shaped magnetic cores. They pack the most power for weight and size, and they make less noise. Toroidal transformers have to be rated at a minimum of several times the intended wattage because the power is delivered in short pulses to the capacitors.

Typically, a Class AB stereo amplifier rated at 200 watts per channel continuously should be capable of delivering 700 watts or so, and this means a transformer rating of about 2000 watts. Anything less means non-continuous operation. This might be alright for a class AB amplifier where maximum continuous operation is not required.

If the stereo amplifier is rated 200 watts per channel pure Class A, it will draw about 1000 watts all the time, meaning that about 3000 watts of power transformer is called for, no less.

Now a toroidal transformer delivers about 30 watts per pound, so a 3000 watt toroid will weight about 100 lbs, maybe more. The rest of such an amplifier will probably weigh about as much, so if you are looking at a 200 watt per channel stereo Class A amplifier, you will want to see if it weighs at least 200 lbs.
One pound of weight for every 2 watts is a good litmus test for evaluating Class A amplifiers. An amplifier weighing less might not be pure Class A. It might be almost Class A, or it might be one of the many products which achieve a Class A designation through trick circuitry.

To lower noise still further, toroids are sometimes encapsulated in metal cans. To reduce magnetic radiation, these cans are usually, but not always, made of steel. This is good, but be aware that in the past, at least one company has used a small transformer in a big can, and made up the difference with sand.

Capacitors
Because of the high capacitance values required, power supply capacitors are almost invariably electrolytic in construction. The capacitors you see in power amplifiers are rated in terms of capacitance in micro-farads, voltage, and current. A typical value for capacitance of one of the big cans is 25,000 micro-farads, or .025 farads. A farad is a big thing; that capacitance which will lose 1 volt after delivering 1 amp for 1 second. In a power amplifier drawing an 8 amp bias, like our 200 watt stereo Class A example, this means a power supply ripple of about .06 volt rms.

Most of the time, you want to see a total of at least 100,000 microfarads, which for our example gives a ripple of about .6 volts. This is pretty good, representing about 1% of the total supply voltage. Smaller amplifiers can get by with less, big amps require more.

Big electrolytic capacitors have a small amount of inductance, or "coilness", in their makeup, a result of the spiral winding of the capacitive film. To reduce the effect of this inductance, film capacitors which have low inductance are often placed in parallel, so that at high frequencies the current flows a little more easily.
An examination of the numbers will provide some insight here. It is common for the inductance of a large electrolytic capacitor to cause its impedance to begin increasing at about 10 KHz so that its impedance is a large fraction of an ohm at 100 KHz. Placing a film cap in parallel will keep the impedance to .1 ohm or so above this frequency.

Is this important because audio has real power at these frequencies? No. Audio has power which declines at about 12 dB/octave above 5 Khz, and real musical slew rate figures are a fraction of a volt per microsecond, meaning that practically no power is needed at 100 KHz.

However, high frequency impedance can be important to the stability of the amplifier, particularly with more complex circuits, as the source impedance of the power supply starts figuring into the feedback at frequencies of a mega-Hertz or so. Interestingly, some designers have depended on a particular source impedance of the supply at these frequencies for stability, thus it is possible to destabilize the amplifier circuit by paralleling film capacitors across the electrolytics. In general, however, film caps in the power supplies are a good sign from the consumer's standpoint.

Inductors
As much as we often try to eliminate inductance in capacitors and wiring, inductors in the form of coils can be used to improve the performance of power supplies. Placing inductance and capacitors on the AC line to form filters will reduce both incoming and outgoing high frequency noise. Large inductors in series with the transformer primaries and secondaries can be used to stretch the duration of the charge pulse to the power supply capacitors, improving regulation and reducing noise. Large inductors in combination with multiple power supply capacitors can form "pi" filters to reduce the noise on the supply lines.
Inductors are very useful, but they cost money. Their use in power amplifier supplies is an indication that the manufacturer has an unusually strong commitment to performance.

Wire
Audiophiles love wire. Perhaps the appeal lies in the accessibility to understanding. Perhaps not. In any case, I like my wire thick and short, and made out of pure soft metals such as copper or silver. I like it terminated tightly and soldered where possible.

Rectifiers
Yeah, sure, rectifiers are important, after all, the AC has to get converted to DC, but I don't like the fast recovery types that some audiophiles have raved about. Fast recovery means that they withstand many amps and volts in a tenth of a few nano-seconds, something we don't see very often on the old 60 Hz AC line. They are essential element in switching power supplies, but for regular "linear" power supplies, I much prefer SLOW diodes, and we create them by placing small capacitor circuits across the diodes, which greatly reduces radiated noise.

Regulation
Active linear regulation is a great way to make the supply voltage constant. Unfortunately it is not usually done properly. In the past, some amplifiers using active regulation have been criticized for a lack of apparent dynamics, and this has given the technique a lesser reputation than it deserves.

Properly done, linear regulation has to go beyond the cursory requirements of the amplifier ratings. The regulator should be capable of ten times the current of the continuous output of the amplifier channel. The regulator should be preceded and followed by large capacitances with values comparable to those needed for unregulated circuits. The transformer size still needs to be as big as that used in an unregulated circuit.
Approached in this manner, linear active regulation delivers the goods.

A far less expensive approach achieves some of the regulation goals, and that is to regulate or otherwise isolate the low power front end of the amplifier, leaving the output stage looking at an unregulated supply. This can be accomplished with entirely separate supplies, active regulation, or with as little as two resistors and two capacitors.

Another way to regulate is by using constant current sources, which feed the circuit a constant current that does not fluctuate with supply voltage. A good constant current source can improve regulation for low power front end circuits by a factor of 100, and combined with supply voltage regulation, gives really excellent performance at little cost.

You can also bias the output stage with a constant high current source to create a single-ended Class A amplifier. I'm not joking.

Switching Supplies
The advantages of switching supplies revolve around low weight, low material cost, and their ability to actively regulate at no additional cost. Noise is a potential problem with switching supplies, but is solvable by physically isolating and filtering the supply, in other words, by spending money.
This can be a deep subject, but suffice it to say that I believe that some of the same caveats apply to switching supplies as linear regulators. Again, they should be rated far beyond the nominal current requirements of the amplifier circuit, particularly as the switchers I have seen usually degrade badly beyond their ratings. Also, it helps if the power supply capacitors before and after the switcher are very substantial. This is typically not the case, since one of the primary motivations to use switchers is to save money.
More sophisticate use of switching circuitry, such as Bob Carver's is more than I would care to tackle here, but you can certainly get a lucid explanation from him.

Mono Operation
We all know what Mono means, which is a one channel amplifier. Of course, for a channel which does not have to share power resources, it mean an improvement, since in a given size box it can have twice as much transformer and capacitor bank. The other intent is to physically and electrically isolate each power amplifier channel from every other, meeting only at the AC line, and sometimes not even there. This way, whatever is happening on one channel has minimal influence on the others.

Mono operation is very desirable in high end systems, but of course it is expensive. A modest compromise is offered by "dual-mono" operation, in which two channels share the same chassis and power cord, but have separate transformers and supply capacitors. This achieves much of the isolation desired at lesser cost.

Battery Operation
Just about total isolation. Near zero noise. Costs a mint.

Conclusion
So what have we learned here? In general it takes big money to buy the big hardware to make really good power amplifier supplies.

Some of the approaches commented on here result in only marginal improvements, but they are measurable. It is not necessary when contemplating these aspects of power supply design to get into a debate of objective versus subjective performance. There is only the issue of how much you are willing to invest in diminishing returns.

Engineering being the science of compromise, each manufacturer draws their own cost/benefit line, and it has been my experience that most manufacturers are quite conscientious about this. The degree of sophistication and massiveness of a supply has the context of the price of the product, and your expectations should be scaled accordingly.

As a consumer, you want the best sound you can get. You can accomplish that through critical listening. As a secondary goal, we all like to get what seems to be good hardware value, and we want to know that that the manufacturer has actually put some real money into the product which costs a small fortune. If you can read the specs or look under the hood, the power supply, being one of the most expensive parts of the amp, usually is a good indicator. It should be the biggest and heaviest part of the amplifier.
What if you don't want to go through the trouble but still want your money's worth? Get at least 15 pounds of amplifier for each thousand dollars spent.

Loudspeakers Lament
Rev 2,July 31, 2013
CLASS A or CLASS A/B……… will Audiophiles ever evolve to a Classless Society?
Is Class A amplification superior and preferred to A/B?

The answers to these two questions are a definitive:
Not Likely
And
Not Always

And the slightly longer answer:
We prefer Class A, because it usually sounds better.
We appreciate Class A/B for it’s practicality.

To illuminate; a very short discussion, not about amplifiers but about one of our other favorite topic, loudspeakers!

When a speaker designer sets about to design a loudspeaker they have a number of physical constraints that they have to work within, and being engineer types we have all sorts of buzzwords that describe those constraints and their effects.

Speaker designers massage those constraints, hopefully to a happy compromise where the speaker achieves various targets, such as frequency response and polar dispersion in your room.

Salient to this discussion would be impedance and “Q”. Most audiophiles have a grasp on impedance, so lets talk very briefly about “Q”.
“Q” describes how a system stores and releases energy and what sort of acoustic artifacts are present at release.

“Q” from a speaker designer perspective has two major subsets:
Qe are the various electrical components of the function
Qm are at the various mechanical components of the function
Collectively they form a loudspeakers “Qts”, the total system “Q”; it’s “Quality Factor”.

The only thing you need to come away with from this is that “quality factor” and “impedance” interact in ways that dramatically shape how a loudspeaker responds to an amplifier and ultimately what we hear from that loudspeaker. As a result some loudspeakers demand wattage, others “not so much”.

And happily we have amplifiers that match to a wide spectrum of speaker characteristics and we can usually predict which amplifier class (A or A/B) behaves best with what speaker……… and so can you.

A moment of audiophile empowerment
When thinking about amplifiers, pick a musical selection that has a combination of great dynamics and inner detail.

My favorite is a Tom Jung (DMP) recording “Tricycle” by Flim and the BB’s (on vinyl) . Old audiophiles will remember this recording! If you have a well recoded personal favorite by all means use that. Maybe something with a great brass section and dramatic dynamic contrast in the lower registers.

At the opening measures of “Tricycle” there is a delicate little instrumental with space and layering; followed by a tremendous crescendo that comes unexpectedly on an up-beat and then falls right back to delicate detail with space and layering.

If upon first listen that crescendo doesn’t startle you, terrify the dog or send the cat and kids scurrying for cover you likely need to pair those speakers with a healthy A/B amplifier (or a much more powerful Class A amplifier)
On the other hand, if there is a lack of space, fine detail and inner depth in that recording, plenty of impact and
no emotion; then you and your speakers may just need a healthy infusion of Class A amplifier power.

If your speaker is efficient and has low impedance (4 ohms or less), you might want to consider Class A first.
IF your speaker is not terribly efficient and is of more conventional impedance (6 ohms or greater) you might want to consider A/B amps first.

It’s about synergy folks…..but you already knew that, right!

Class A amplifiers bring delicate control to the listening experience. Class A/B amplifiers bring a certain speed and jump to the listening experience in a smaller package.

Having a choice between Class A and Class A/B amplification is another tool to optimize your listening experience……

Our Customers Opine!
We have our favorites, and so do you! Call us at +1.530.367.3690 if you have specific speakers you want to discuss with us.

Without mentioning names:
Electrostatic panel aficionados adore amplifiers with output voltage to spare. Big voltage in a practical amplifier, the logical choice is A/B and for those duties the Pass Labs X600.5 and X1000.5 reign supreme.
Planar magnetic speakers, another panel speaker, but very unlike most electrostatic designs in their amplifier requirements. Planar speakers appreciate power, but they do not absolutely demand power. What you are going to want is at least 100 of the best watts you can afford. Class A power preferred, it simply sounds better. If XA100.5’s are outside of the budget, then the X350.5 or X250.5 can be used to good effect. For the smallest planar magnetic panels in either a surround or small second system an X150.5.

Highly efficient large floor standing conventional paper cone loudspeakers; we’ve been frequently informed that “Magic Happens” when these speakers are driven by the XA-60.5 Class A monobloc’s. An XA-30.5 stereo amp is another excellent choice, but typically does not deliver quite as deep a soundstage or quite as much bass foundation as the XA60.5

Contrasted to cone loudspeakers that are not so large, those with multiple small to medium size woofers a couple of midrange drivers, metal dome tweeters. Loudspeakers of very low efficiency, frequently difficult to drive beyond 105 dB, in room. Usually these sound best when they have high wattage amplifiers at their disposal. The cognoscenti opt for either the X600.5 or XA200.5 Those with the wherewithal overwhelmingly prefer the Xs-300.5. The Xs-300.5’s having the spatial richness of Class A and the drive normally reserved for Class A/B amplifiers.

Legendary in the UK, and once again gaining popularity worldwide, moderately large easy to drive box speakers of modest power requirements. What too choose, anything XA.5 or Xs from the diminutive Xa30.5 on up.

Studio monitor loudspeakers, those with professional recording studio pedigree’s usually demand power. At minimum Xa-160.5 monobloc’s. For a big room and the ability to listen at concert level, X600.5 monobloc’s may be a better choice at an equivalent price-point.

At the end of the day all speakers require power to behave as intended. Some require all the power you can muster, others more modest.

We prefer the sound of our Class A designs. IF the space or budget will not support our Class A designs the A/B product will supply the power in a smaller more affordable package without giving up too much in the way of performance.

Class A watts are hardware heavy, not all systems and budgets will support that level of hardware. For those systems we have very high performance A/B amplifiers.